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Emergency allergy shots less effective after heat exposure

(Reuters Health) – – The medicine in emergency allergy shots like the EpiPen can deteriorate when exposed to heat, so don’t leave them in the car on a hot day, researchers warn.

FILE PHOTO: EpiPen auto-injection epinephrine pens manufactured by Mylan NV pharmaceutical company for use by severe allergy sufferers are seen in Washington, U.S. August 24, 2016. REUTERS/Jim Bourg/File Photo

Patients with serious allergies typically carry an emergency autoinjector – such as the EpiPen made by drugmaker Mylan NV – at all times. The devices are used to deliver an emergency dose of the hormone epinephrine to patients who may go into life-threatening anaphylactic shock.

“We work with hundreds of patients with histories of anaphylaxis, who carry epinephrine on a daily basis,” lead author Piotr Lacwik, who works at the Medical University of Lodz in Poland, said in an email. “I noticed that not all of them have their epinephrine on them at all times and, alarmingly, some leave injectors in the car.”

For the study, Lacwik and his team purchased 12 EpiPen Senior injectors from the same lot to ensure consistency. They distributed nine EpiPens between the glove compartment, cabin shelf and trunk of a car parked in a treeless area. The remaining three were stored in a dark, air-conditioned room at a constant temperature.

After half a day, the researchers retrieved the EpiPens from the car and cooled them to room temperature before testing their contents.

They found that the concentration of epinephrine in the autoinjectors was reduced by 3.3 percent in samples placed in the trunk, 13.3 percent in those placed in the cabin and 14.3 percent in those left in the glove compartment.

Most guidelines recommend 0.3 mg or 0.5 mg as an initial dose for an adult. Because the EpiPen Senior has a total dose of 0.3 mg, any deterioration puts the dose below the recommended threshold, Lacwik said.

The EpiPens in the glove compartment were noticeably warm to the touch when retrieved, researchers noted. This was because the enclosed space likely reduced the dissipation of heat even when ambient temperatures began to drop, they explain in The Journal of Allergy and Clinical Immunology: In Practice.

Paradoxically, epinephrine in low concentrations can worsen anaphylaxis, the authors write, but Lacwik notes the decreases seen after a single exposure to heat in the study are unlikely to produce that effect.

A spokeswoman for Mylan said that while the company was not involved in the study, “its findings are consistent with the storage guidelines outlined in the FDA-approved label for EpiPen Auto-Injector.”

“Per the label, EpiPen Auto-Injector is to be stored at 20°C to 25°C (68°F to 77°F),” she said.

The report notes that although prescribing and patient information available online includes a warning against glovebox storage of EpiPens, the leaflet enclosed with the devices did not.

Allergist Dr. Purvi Parikh, spokeswoman for the Allergy and Asthma Network, pointed out that the study tested only one brand of autoinjectors, in only one make and model of car. Still, she called the results “concerning,” as many patients keep their autoinjectors in their cars for convenience.

“Patients likely are not aware of this risk in general and need to be advised,” Parikh, who was not involved in the study, told Reuters Health.

“With anaphylaxis, timing of epinephrine dosing is crucial in saving lives and so if the epinephrine is ineffective (it) can be deadly for patients.”

Lacwik too said the results might not translate precisely to other formulations of epinephrine in other climates or car models. But “while our study did not check any of those alternatives, we believe that the general conclusion- a warning against leaving autoinjectors in the heat – can be applied to all formulations of epinephrine available on the market,” he said.

SOURCE: The Journal of Allergy and Clinical Immunology: In Practice, online November 28, 2018.

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